/**
 * 给指定页面添加背景水印
 */
function addWaterMarker(str, parentNode, font, textColor) {
    // 水印文字，父元素，字体，文字颜色
    var can = document.createElement('canvas');
    parentNode.appendChild(can);
    can.width = 200;
    can.height = 150;
    can.style.display = 'none';
    var cans = can.getContext('2d');
    cans.rotate((-20 * Math.PI) / 180);
    cans.font = font || '16px Microsoft JhengHei';
    cans.fillStyle = textColor || 'rgba(180, 180, 180, 0.3)';
    cans.textAlign = 'left';
    cans.textBaseline = 'Middle';
    cans.fillText(str, can.width / 10, can.height / 2);
    parentNode.style.backgroundImage = 'url(' + can.toDataURL('image/png') + ')';
}

const waterMarker = {
    bind: function (el, binding) {
        addWaterMarker(binding.value.text, el, binding.value.font, binding.value.textColor);
    }
};

export default waterMarker;
